1. Field of the Invention
The present invention relates to a structure to attach optical fibers to a photoelectric switch in which optical fibers are used in a sensor section.
2. Related Background Art
In a photoelectric switch using optical fibers, for instance, as disclosed in Japanese Utility Model Registration Application Laid-open Publication No. 62-10342, a structure for attaching optical fibers to a photoelectric switch has been proposed. According to such a structure, as shown in FIGS. 8 and 9, a supporting portion 4 having grooves 4a and 4b each of which has a half circle-shaped cross section which are communicated with optical fiber inserting ports 2 and 3 is projected from an end portion of a casing 1 of the photoelectric switch. A fastening frame 5 which is attached to the supporting portion 4 is provided. A groove 5b having a half circle-shaped cross section and corresponding to the groove 4b is formed on the inner wall of the frame 5. A protection cover 6 having a space enough to enclose the fastening frame 5 and having openings 6a and 6b at the positions corresponding to the optical fiber inserting ports 2 and 3 is fixed to the casing 1 by fixing means (not shown). Optical fibers 7a and 7b are inserted into the openings 6a and 6b. An arc-shaped pressing metal fitting 8 is put onto the supporting portion 4. The pressing metal fitting 8 is fastened to the frame 5 by a fastening screw 9, thereby fixing the optical fibers 7a and 7b.
According to such a conventional optical fiber attaching structure of the photoelectric switch, the arc-shaped pressing metal fitting 8 covers a part of the optical fiber inserting port 2 and becomes an obstacle, so that there is a drawback such that it is difficult to insert the optical fibers and it is troublesome to attach them.